While high-efficiency multijunction solar cells are commonly used for space satellites, researchers have continued to look for ways to improve cost and performance to enable a broader range of applications.

The IMM technique licensed by MicroLink Devices enables multijunction III-V solar cells to be grown with both higher efficiencies and lower costs than traditional multijunction solar cells by reversing the order in which individual sub-cells are typically grown.

The IMM architecture enables greater power extraction from the higher-bandgap sub-cells and further allows the use of more efficient low-bandgap sub-cell materials such as Indium Gallium Arsenide.

In contrast to traditional III-V multijunction solar cells, IMM devices are removed from their growth substrate, allowing the substrate to be reused over multiple growth runs – a significant component in reducing overall device costs. Removing the substrate also reduces the weight of the solar cell, which is important for applications such as solar-powered unmanned aerial vehicles.

By utilizing its ELO capabilities, MicroLink will be able to make thin, lightweight, and highly flexible IMM solar cells which are ideal for use in unmanned aerial vehicles, space-based vehicles and equipment, and portable power generation applications.

“IMM makes multijunction solar cells practical for a wide variety of weight-, geometry-, and space-constrained applications where high efficiency is critical,” said Jeff Carapella, one of the researchers in NREL’s III-V multijunction materials and devices research group that developed the technology.

“Former NREL Scientist Mark Wanlass pioneered the use of metamorphic buffer layers to form tandem III-V solar cells with three or more junctions.

This approach is very synergistic with our ELO process technology, and MicroLink Devices is excited to now be commercializing IMM solar cells for high-performance space and UAV applications,” said Noren Pan, CEO of MicroLink Devices.

MicroLink and NREL have collaborated to evaluate the use of ELO for producing IMM solar cells since 2009, when MicroLink was the recipient of a DOE PV Incubator subcontract from NREL.

NREL has more than 800 technologies available for licensing and continues to engage in advanced research and development of next-generation IMM and ultra-high-efficiency multijunction solar cells with both academic and commercial collaborators.

Companies interested in partnering to advance research on or commercialize renewable energy technologies can visit the EERE Energy Innovation Portal, which features descriptions of all renewable energy technologies funded by the DOE’s Office of Energy Efficiency and Renewable Energy.

Parties interested specifically in ongoing development of IMM solar cells can contact Dan Friedman, Manager of NREL’s High Efficiency Crystalline Photovoltaics Group, for more information.

NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.

James Baker, Business Director for Graphene at The University of Manchester, talks to AZoNano about the current state of the graphene market and the key next steps needed.

When we last spoke back in 2015 the National Graphene Institute (NGI) had been focused on the successful commercialisation of graphene through collaborative work between research and industry. How has the graphene community developed since then?

The University of Manchester (UoM) now has over 250 researchers working on graphene and 2D materials and the National Graphene Institute (NGI) has now been open for over 2 years. The NGI has provided a key facility and capability in bringing together the multi-disciplinary research from across the University together with developing partnerships and collaborations with industry to accelerate the development of graphene products and applications.

We are also close to opening our second graphene building, the Graphene Engineering Innovation Centre, next year. This will allow the University to create a unique hub for 2D materials knowledge and commercialisation in Manchester alongside close links with industry.

The graphene roadmap was a crucial part of the conversation two years ago. Where do you think the industry currently stands in-line with these predictions?

Road-mapping is a key part of the commercialisation journey but I am now seeing a much more significant “applications pull” from industry which is resulting in increasing engagement of activity and translation into projects and the development of new graphene enhanced concepts and applications.

You recently spoke about commercialisation at Graphene Week 2017. What were the key areas of discussion this year?

As always there is a significant amount of new science being presented at Graphene Week, but there was also evidence of industry now starting to get “interesting” and “beneficial” results from their engagements and projects involving graphene with a significant amount of progress having taken place over the past two years.

A common challenge when attempting to make a graphene-based sensor is the high levels of electronic noise that are caused, reducing its effectiveness. In a recent work, an international team of researchers proposed a graphene-based semiconductor device that reduces electronic noise when its electric charge is neutral (referred to as its neutrality point). The group achieved this neutrality point without the need for bulky magnetic equipment that had previously prevented these approaches from being used in portable sensor applications.

In a proof-of-concept device, the researchers used their new sensing scheme to detect HIV-related DNA hybridization at picomolar concentrations. The team fabricated a charge detector out of graphene that can detect very small amounts of charges close to its surface. The sensing principle of the device relies on charge species detection through the field-effect, which brings about a change in electrical conductance of graphene upon adsorption of a charged molecule on the sensor surface.

“Graphene is perfect for such application,” explained members of the team. “Graphene is unique among other solid-state materials in that all carbon atoms are located on the surface, making the graphene surface highly sensitive for detection of changes in the environment.”

However, the team notes that the ability to create practical electrochemically gated graphene-based field-effect transistors to detect charged species also requires a small amount of electronic noise, the existence of which fundamentally limits a sensor’s resolution.

“I believe we have discovered an elegant and simple approach to improve the sensitivity of next generation graphene electronic biochemical sensor devices,” said the team. “Our device is able to function at its low-noise neutrality point without the need for complicated magnetic equipment that other approaches using graphene have depended upon.”

The researchers add that electronic noise can be reduced without compromising the sensing response, enabling significant improvement to the signal-to-noise ratio compared to that of a conventionally operated graphene transistor to measure conductance. This noise reduction and maintaining of the sensing response is achieved by making use of one of the unique properties of graphene field-effect transistors: its ambipolar (being both n- or p-type) behavior near the neutrality point.

This neutrality point appears in graphene as the lowest point of conductance in the material and is the result of graphene’s unique electronic band structure. At this low conductance point, the graphene sensors can operate at a lower noise level. While this doesn’t compromise the sensing response, it does lower the signal-to-noise ratio of the device, resulting in an overall improved sensing response.

Another feature of the latest device is the use of so-called in-situ ‘electrochemical cleaning’ to ensure a clean graphene surface, which is a new technique meant to enable graphene electronic biosensors to provide reliable performance.
While they were able to test their sensing scheme on HIV, more work must be done before this device could find its way into the next generation of biochemical sensors.

First of all, the team believes that there is a need to scale up the miniaturized graphene electronic arrays. In addition, microfluidic or nanofludic liquid handling should also be integrated into the arrays.

There will also be a need for on-site electrochemical cleaning on each of the devices and the more surface functionalization to suit different cases of biomolecule detection.

The researchers intend to adopt this low-noise technology for other single molecule detection methods and evaluate the sensor performances when scaled up.

Like this:

Solar-excited “hot” electrons are usually wasted as heat in conventional silicon solar cells. In a new type of solar cell, known as a hybrid organic-inorganic perovskite cell, scientists found these “hot” electrons last longer. These hot electrons have lifetimes more than a 1000 times longer than those formed in silicon cells.

In the illustration of a perovskite structure, a “hot” electron is located at the center of the image. Positive molecules (red and blue dumbbells) surround the “hot” electron. The distortion of the crystal structure and the liquid-like environment of the positive molecules (blurred dumbbells at the periphery of the image) screen (yellow circle, partially shown) the “hot” electron. The “shield” protects the hot electron and allows it to survive 1000 times longer than it would in conventional silicon solar cells. (Image: Xiaoyang Zhu, Columbia University)

This research identified a possible route to dramatically increase the efficiency of solar cells. By slowing the cooling of excited “hot” electrons, scientists could produce more electricity. They could devise cells that function above the predicted efficiency limit, around 33 percent, for conventional solar cells.

Hybrid organic-inorganic lead halide perovskites (HOIP) are promising new materials for use in low-cost solar cells. HOIPs have already been demonstrated in solar cells with solar-to-electricity conversion efficiency exceeding 20 percent, which is on par with the best crystalline silicon solar cells.

Research is ongoing to discover why HOIPs work so well for solar energy harvesting and to determine their efficiency limit. A team led by Columbia University has discovered that electrons in HOIPs acquire protective shields that make them nearly invisible to defects and other electrons, which allows the electrons to avoid losing energy. The mechanism of protection is dynamic screening correlated with liquid-like molecular motions in the crystal structure.

Moreover, the researchers discovered that the protection mechanism works for electrons with excess energy (with energy greater than the semiconductor band gap); as a result, these so-called “hot” electrons are very long-lived in HOIPs. In a conventional solar cell, such as the silicon cell widely in use today, only part of the solar spectrum is used, and the energy of the “hot” electrons is wasted. Excess electron energy generated initially from the absorption of high-energy photons in the solar spectrum is lost as heat before the electron is harvested for electricity production.

For conventional solar cells, this loss is partially responsible for the theoretical efficiency limit of around 33 percent, called the Shockley-Queisser limit. However, the long lifetime of “hot” electrons in HOIPs makes it possible to harvest the “hot” electrons to produce electricity, thus increasing the efficiency of HOIP solar cells beyond the conventional limit.

Shortening recharge times may diminish range anxiety, increase EV market viability, howeverSpeeding up battery charging will be crucial to improving the convenience of owning and driving an electric vehicle (EV).

The Energy Department’s National Renewable Energy Laboratory (NREL) is collaborating with Argonne National Laboratory (ANL), Idaho National Laboratory (INL), and industry stakeholders to identify the technical, infrastructure, and economic requirements for establishing a national extreme fast charging (XFC) network.

Today’s high power EV charging stations take 20 minutes or more to provide a fraction of the driving range car owners get from 10 minutes at the gasoline pump.

Porsche is leading the industry with the deployment of two XFC 350kW EV charging stations in Europe thatwill begin to approach the refueling time of gasoline vehicles. Photo courtesy of Porsche.

Drivers can pump enough gasoline in 10 minutes to carry them a few hundred miles. Most of today’s fast charging stations take 20 minutes to provide 50-70 miles of electric driving range.

A series of articles in the current edition of the Journal of Power Sources summarizes the NREL team’s findings on how battery, vehicle, infrastructure, and economic factors impact XFC feasibility.

“You can charge an EV today at one of 44,000 stations across the country, but if you can’t leave your car plugged in for a few hours, you may only get enough juice to travel across town a few times,” says NREL Senior Engineer and XFC Project Lead Matthew Keyser.

“We’re working to match the time, cost, and distance that generations of drivers have come to expect—with the additional benefits of clean, energy-saving technology.”

While XFC can help overcome real (and perceived) EV driving range limitations, the technology also introduces a series of new challenges. More rapid and powerful charging generates higher temperatures, which can lead to battery degradation and safety issues.

Power electronics found in commercially available EVs are built for slower overnight charging and may not be able to withstand the stresses of higher voltage battery systems which are expected for higher power charging systems. XFC’s extreme, intermittent demands for electricity could also pose challenges to grid stability.

The XFC research team is exploring solutions for these issues, examining factors related to vehicle technology, gaps in existing technology, new demands on system design, and additional thermal management requirements. Researchers are also looking beyond vehicle systems to consider equipment and station design and potential impact on the grid.

NREL’s intercity travel analysis revealed that recharge times comparable to the time it takes to pump gas will require charge rates of at least 400 kW. Current DC Fast Charging rates are limited to 50-120 kW, and most public charging stations are limited to 7kW.

XFC researchers have concluded that this will necessitate increases in battery charging density and new designs to minimize potential related increases in component size, weight, and cost.

It appears that a more innovative battery thermal management system will be needed if XFC is to become a reality, and new strategies and materials will be needed to improve battery cell and pack cooling, as well as the thermal efficiency of cathodes and anodes.

“Yes, this substantial increase in charging rate will create new technical issues, but they are far from insurmountable—now that we’ve identified them,” says NREL Engineer Andrew Meintz.

Development of a network of XFC stations will depend on cost, market demand, and management of intermittent power demands.
The team’s research revealed a need for more extensive analysis of potential station siting, travel patterns, grid resources, and business cases.

At the same time, it is clear that any XFC network will call for new infrastructure technology and operational practices, along with cooperation and standardization across utilities, station operators, and manufacturers of charging systems and EVs.

These studies provide an initial framework for effectively establishing XFC technology. The initiative has attracted keen interest from industry members, who realize that faster charging will ultimately lead to wider market adoption of EV technologies.

This research is supported by the DOE Vehicle Technologies Office. Learn more about NREL’s energy storage and EV grid integration research.

NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.

A concept truck by Toyota is powered by hydrogen fuel cells and emits nothing but water vapor. Photo Credit: Toyota

Vehicles powered by alternatives to fossil fuel are on the roll. Literally. The Japanese automaker Toyota is rolling out a new line of vehicles powered by hydrogen fuel cells. A concept version of a long-haul truck with the car manufacturer’s new hydrogen-based engine in it will set out with a full load of cargo from Los Angeles and make its way to Long Beach.

“If you see a big-rig driving around the Ports of Los Angeles and Long Beach that seems oddly quiet and quick, do not be alarmed! It’s just the future,” Toyota quips in a statement issued to the press. The trial is part of the Japanese company’s feasibility studies for its brand-new “Project Portal” – a hydrogen fuel cell systemdesigned for heavy-duty trucks. Toyota touts its Project Portal as the next step in its development of zero-emission fuel cell technology for industrial uses.

“[The trial’s] localized, frequent route patterns are designed to test the demanding drayage duty-cycle capabilities of the fuel cell system while capturing real world performance data,” Toyota explains of its upcoming test runs. “As the study progresses, longer haul routes will be introduced.”

Toyota’s heavy-duty concept truck boasts a beast of an engine with more than 670 horsepower and 1,325 pound feet of torque thanks to a pair of Mirai fuel cell stacks and a relatively small 12kWh battery. The truck’s gross weight capacity is over 36,000kg while its projected driving range is more than 320km per fill under normal drayage conditions.

Comparable long-haul trucks, if powered by gasoline, emit plenty of CO2. Not this new one, though. “The zero-emission class 8 truck proof of concept has completed more than 4,000 successful development miles, while progressively pulling drayage rated cargo weight, and emitting nothing but water vapor,” the company explains.

You’ve read that right: the truck will emit water vapor and nothing else. This means that the technology, once it is put into use on a wider scale, can help us reduce our CO2 emissions in an effort to mitigate the effects of climate change.

Lithium-ion batteries are used to power many things from mobile phones, laptops, tablets to electric cars. But they have some drawbacks, including limited energy storage capacity, low durability and long charging time.

Now, researchers at the Institute of Bioengineering and Nanotechnology (IBN) at Singapore’s Agency for Science, Technology and Research (A*STAR) have developed a way of producing more durable and longer lasting lithium-ion batteries. This finding was reported in Advanced Materials. Led by IBN Executive Director Professor Jackie Y. Ying, the researchers invented a generalized method of producing anode materials for lithium-ion batteries. The anodes are made from metal oxide nanosheets, which are ultrathin, two-dimensional materials with excellent electrochemical and mechanical properties.

These nanosheets are 50,000 times thinner than a sheet of paper, allowing faster charging of power compared to current battery technology. The wide surface area of the nanosheets makes better contact with the electrolyte, thus increasing the storage capacity. The material used is also highly durable and does not break easily, which improves the battery shelf life. Existing methods of making metal oxide nanosheets are time-consuming and difficult to scale up.

The IBN researchers came up with a simpler and faster way to synthesize metal oxide nanosheets using graphene oxide. Graphene oxide is a 2D carbon material with chemical reactivity that facilities the growth of metal oxides on its surface. Graphene oxide was used as the template to grow metal oxides into nanosheet structures via a simple mixing process, followed by heat treatment. The researchers were able to synthesize a wide variety of metal oxides as nanosheets, with control over the composition and properties. The new technique produces the nanosheets in one day, compared to one week for previously reported methods.

It does not require the use of a pressure chamber and involves only two steps in the synthesis process, making the nanosheets easy to manufacture on a large scale. Tests showed that the nanosheets produced using this generalized approach have excellent lithium-ion battery anode performance, with some materials lasting three times longer than graphite anodes used in current batteries. “Our nanosheets have shown great promise for use as lithium-ion anodes.

This new method could be the next step toward the development of metal oxide nanosheets for high performance lithium-ion batteries. It can also be used to advance other applications in energy storage, catalysis and sensors,” said Ying.

The article can be found at: AbdelHamid et al. (2017) Generalized Synthesis of Metal Oxide Nanosheets and Their Application as Li-Ion Battery Anodes. ——— Source: A*STAR.

Research in lithium-ion batteries has opened up a plethora of possibilities in the development of next-generation batteries. In particular, the metal-air batteries with significantly greater energy density close to that of gasoline per kilogram, has recently been acknowledged and invested by world’s leading companies, like IBM.

A recent study, affiliated with UNIST has presented novel catalyst to accelerate the commercialization of metal-air batteries. This breakthrough has been jointly led by Professor Guntae Kim and Professor Jaephil Cho in the School of Energy and Chemical Engineering at UNIST in collaboration with Professor Yunfei Bu from Nanjing University of Science and Technology, Nanjing, China. Their new catalyst possesses the structure of nanofiber-based perovskite materials and exhibits excellent electrochemical performance, close that of today’s precious metal catalysts, yet still inexpensive.

A metal-air battery is a type of fuel cell or battery that uses the oxidation of a metal with oxygen from atmospheric air to produce electricity. It is equipped with an anode made up of pure metals–like lithium or zinc–and an air cathode that is connected to an inexhaustible source of air. The catalysts in the air cathode aids the electrochemical reaction of the cell with oxygen gas. Metal-air batteries have attracted significant research attention as the new generation of high-performance batteries as they the advantages of (1) simple structure, (2) extremely high energy density, and (3) a relatively inexpensive production.

The currently existing metal-air batteries use rare and expensive metal catalysts for their air electrodes, such as platinum (Pt) and iridium oxide (IrO?). This has hindered its further commercialization into the marketplace.

In the study, Professor Kim and his research team have developed a new catalyst, using the cation ordered double perovskite with high electrical conductivity and catalyic performance. They prepared a series of PrBa0.5Sr0.5Co2-xFexO5+δ (x = 0, 0.5, 1, 1.5, and 2, PBSCF) and determined the optimum cobalt (Co) and iron (Fe) contents through electrochemical evaluation.

“The structure of mesoporous PrBa0.5Sr0.5Co2-xFexO5+δ nanofiber (PBSCF-NF) has high surface areas, result from uniform pore diameters,” says Ohhun Gwon in the Combined M.S/Ph.D. of Energy and Chemical Engineering, the first author of the study. “This nanofiber has also brought significant improvements in the performance of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).”

According to the research team, this nanofiber has improved the bi-functionality of ORR/OER. Particularly, the OER performance was about 9 times higher than that of state-of-the-art precious metal oxide IrO2 at overpotential of 0.3 V. Furthermore, it also demonstrated notable charge-discharge stability even at high current density in Zn-air batteries.

“We envision that the high electrochemical and catalytic performance of this material will play a major role in the commercialization of metal-air batteries,” says Professor Kim. “Metal-air battery technology is still in its infancy and extensive additional research efforts appear to be required before a viable commercial implementation is developed.”

He adds, “However, as many global corporates, such as IBM, Toyota, and Samsung Electronics are already working on the development of metal-air batteries, the technical challenges could soon be cleared out in a much faster pace than anticipated.”

###

The findings of the research have been published online in the October issue of the prestigious journal ACS Nano. This study has been supported by the Mid-Career Researcher Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT and Future Planning and 2017 Research Fund of UNIST.

Beijing’s announcement that it is considering banning gasoline and diesel cars from its smog clogged roads promises to accelerate a push toward electric vehicles — a race in which Chinese car makers have everything to gain.

Even as the power of our modern computers grows exponentially, biological systems — like our brains — remain the ultimate learning machines.

By finding materials that act in ways similar to the mechanisms that biology uses to retain and process information, scientists hope to find clues to help us build smarter computers.

Inspired by human forgetfulness — how our brains discard unnecessary data to make room for new information — scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory, in collaboration with Brookhaven National Laboratory and three universities, conducted a recent study that combined supercomputer simulation and X-ray characterization of a material that gradually “forgets.” This could one day be used for advanced bio-inspired computing.

“It’s hard to create a non-living material that shows a pattern resembling a kind of forgetfulness, but the specific material we were working with can actually mimic that kind of behavior.” –

Subramanian Sankaranarayanan, Argonne nanoscientist at ANL teams up with the study’s author.

“The brain has limited capacity, and it can only function efficiently because it is able to forget,” said Subramanian Sankaranarayanan, an Argonne nanoscientist and study author. “It’s hard to create a non-living material that shows a pattern resembling a kind of forgetfulness, but the specific material we were working with can actually mimic that kind of behavior.”

The material, called a quantum perovskite, offers researchers a simpler non-biological model of what “forgetfulness” might look like on an electronic level.
The perovskite shows an adaptive response when protons are repeatedly inserted and removed that resembles the brain’s desensitization to a recurring stimulus.

Quantum simulations performed at the Argonne Leadership Computing Facility (ALCF), a DOE Office of Science User Facility, probed the origin of this adaptive response.

“When scientists add or remove a proton (H+) from the perovskite (SmNiO3 (SNO)) lattice, the material’s atomic structure expands or contracts dramatically to accommodate it in a process called ‘lattice breathing,'” said Badri Narayanan, an Argonne assistant material scientist and co-author of the study. But when this happens over and over again, the material’s behavior evolves such that the lattice breathing is reduced — the proton “threat” no longer causes the material to hyperventilate. “The material’s electronic properties also evolve with this process,” said Narayanan.

“Eventually, it becomes harder to make the perovskite ‘care’ if we are adding or removing a proton,” said Hua Zhou, a physicist involved in characterizing the behavior of the material using X-rays provided by Argonne’s Advanced Photon Source (APS), a DOE Office of Science User Facility. “It’s like when you get very scared on a water slide the first time you go down, but each time after that you have less and less of a reaction.”

As the material responds to protons that scientists add and subtract, its ability to resist an electrical current can be severely affected. This behavior allows the material to be effectively programmed, like a computer, by the proton doping. Essentially, a scientist could insert or remove protons to control whether or not the perovskite would allow a current.

Researchers have recently pushed to develop non-silicon-based materials, like perovskites, for computing because silicon struggles to use energy as efficiently. Scientists may use perovskites in learning machines down the line. But scientists can also take advantage of perovskite properties by using them as the basis for computational models of more complex biological learning systems.

“These simulations, which quite closely match the experimental results, are inspiring whole new algorithms to train neural networks to learn,” said Mathew Cherukara, an Argonne postdoctoral scholar at the APS.

The perovskite material and the resulting neural network algorithms could help develop more efficient artificial intelligence capable of facial recognition, reasoning and human-like decision making. Scientists are continuing the research to discover other materials with these brain-like properties and new ways to program these materials.

Finally, unlike silicon, whose properties can be reliably described using simple computer models, understanding the perovskite material requires computationally intensive simulations to capture how its atomistic and electronic structure reacts to proton doping.

“A classical framework doesn’t apply to these complex systems,” said Sankaranarayanan who, along with Narayanan and Cherukara, modeled the perovskite’s behavior at Argonne’s Center for Nanoscale Materials, a DOE Office of Science User Facility, and the ALCF. “Quantum effects dominate, so it takes very computationally demanding simulations to show how the proton moves in and out of the perovskite structure.”

Also Read:

Habituation based synaptic plasticity and organismic learning in a quantum perovskite